2019-11-20 18:44:28

by Petr Vorel

Subject: [nfs-utils PATCH 1/1] mount: Do not overwrite /etc/mtab if it's symlink

From: Joey Hess <[email protected]>

Some systems have /etc/mtab symlink to /proc/mounts. In that case
mount.nfs complains:
Can't set permissions on mtab: Operation not permitted

See https://bugs.debian.org/476577

This change makes mount.nfs handle symlinked /etc/mtab the way
umount.nfs and util- linux handle it.

Cc: Chuck Lever <[email protected]>
Signed-off-by: Joey Hess <[email protected]>
[ pvorel: took patch from Debian, rebased for 2.4.3-rc1 and created commit
message. Patch is also used in Gentoo. ]
Signed-off-by: Petr Vorel <[email protected]>
---
Hi,

if you merge, please keep Joey as the author in git :).

Kind regards,
Petr

utils/mount/fstab.c | 2 +-
utils/mount/fstab.h | 1 +
utils/mount/mount.c | 7 +++++++
3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/utils/mount/fstab.c b/utils/mount/fstab.c
index 8b0aaf1a..146d8f40 100644
--- a/utils/mount/fstab.c
+++ b/utils/mount/fstab.c
@@ -61,7 +61,7 @@ mtab_does_not_exist(void) {
return var_mtab_does_not_exist;
}

-static int
+int
mtab_is_a_symlink(void) {
get_mtab_info();
return var_mtab_is_a_symlink;
diff --git a/utils/mount/fstab.h b/utils/mount/fstab.h
index 313bf9b3..8676c8c2 100644
--- a/utils/mount/fstab.h
+++ b/utils/mount/fstab.h
@@ -7,6 +7,7 @@
#define _PATH_FSTAB "/etc/fstab"
#endif

+int mtab_is_a_symlink(void);
int mtab_is_writable(void);
int mtab_does_not_exist(void);
void reset_mtab_info(void);
diff --git a/utils/mount/mount.c b/utils/mount/mount.c
index 91f10877..92a0dfe4 100644
--- a/utils/mount/mount.c
+++ b/utils/mount/mount.c
@@ -204,6 +204,13 @@ create_mtab (void) {
int flags;
mntFILE *mfp;

+ /* Avoid writing if the mtab is a symlink to /proc/mounts, since
+ that would create a file /proc/mounts in case the proc filesystem
+ is not mounted, and the fchmod below would also fail. */
+ if (mtab_is_a_symlink()) {
+ return EX_SUCCESS;
+ }
+
lock_mtab();

mfp = nfs_setmntent (MOUNTED, "a+");
--
2.24.0

2019-11-20 18:53:51

by Chuck Lever III

Subject: Re: [nfs-utils PATCH 1/1] mount: Do not overwrite /etc/mtab if it's symlink

> On Nov 20, 2019, at 1:35 PM, Petr Vorel <[email protected]> wrote:
>
> From: Joey Hess <[email protected]>
>
> Some systems have /etc/mtab symlink to /proc/mounts. In that case
> mount.nfs complains:
> Can't set permissions on mtab: Operation not permitted
>
> See https://bugs.debian.org/476577
>
> This change makes mount.nfs handle symlinked /etc/mtab the way
> umount.nfs and util- linux handle it.
>
> Cc: Chuck Lever <[email protected]>

No objection from me.


> Signed-off-by: Joey Hess <[email protected]>
> [ pvorel: took patch from Debian, rebased for 2.4.3-rc1 and created commit
> message. Patch is also used in Gentoo. ]
> Signed-off-by: Petr Vorel <[email protected]>
> ---
> Hi,
>
> if you merge, please keep Joey as the author in git :).
>
> Kind regards,
> Petr
>
> utils/mount/fstab.c | 2 +-
> utils/mount/fstab.h | 1 +
> utils/mount/mount.c | 7 +++++++
> 3 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/utils/mount/fstab.c b/utils/mount/fstab.c
> index 8b0aaf1a..146d8f40 100644
> --- a/utils/mount/fstab.c
> +++ b/utils/mount/fstab.c
> @@ -61,7 +61,7 @@ mtab_does_not_exist(void) {
> return var_mtab_does_not_exist;
> }
>
> -static int
> +int
> mtab_is_a_symlink(void) {
> get_mtab_info();
> return var_mtab_is_a_symlink;
> diff --git a/utils/mount/fstab.h b/utils/mount/fstab.h
> index 313bf9b3..8676c8c2 100644
> --- a/utils/mount/fstab.h
> +++ b/utils/mount/fstab.h
> @@ -7,6 +7,7 @@
> #define _PATH_FSTAB "/etc/fstab"
> #endif
>
> +int mtab_is_a_symlink(void);
> int mtab_is_writable(void);
> int mtab_does_not_exist(void);
> void reset_mtab_info(void);
> diff --git a/utils/mount/mount.c b/utils/mount/mount.c
> index 91f10877..92a0dfe4 100644
> --- a/utils/mount/mount.c
> +++ b/utils/mount/mount.c
> @@ -204,6 +204,13 @@ create_mtab (void) {
> int flags;
> mntFILE *mfp;
>
> + /* Avoid writing if the mtab is a symlink to /proc/mounts, since
> + that would create a file /proc/mounts in case the proc filesystem
> + is not mounted, and the fchmod below would also fail. */
> + if (mtab_is_a_symlink()) {
> + return EX_SUCCESS;
> + }
> +
> lock_mtab();
>
> mfp = nfs_setmntent (MOUNTED, "a+");
> --
> 2.24.0
>

--
Chuck Lever

2019-11-22 15:50:05

by Steve Dickson

Subject: Re: [nfs-utils PATCH 1/1] mount: Do not overwrite /etc/mtab if it's symlink

On 11/20/19 1:35 PM, Petr Vorel wrote:
> From: Joey Hess <[email protected]>
>
> Some systems have /etc/mtab symlink to /proc/mounts. In that case
> mount.nfs complains:
> Can't set permissions on mtab: Operation not permitted
>
> See https://bugs.debian.org/476577
>
> This change makes mount.nfs handle symlinked /etc/mtab the way
> umount.nfs and util- linux handle it.
>
> Cc: Chuck Lever <[email protected]>
> Signed-off-by: Joey Hess <[email protected]>
> [ pvorel: took patch from Debian, rebased for 2.4.3-rc1 and created commit
> message. Patch is also used in Gentoo. ]
> Signed-off-by: Petr Vorel <[email protected]>
Committed... (tag: nfs-utils-2-4-3-rc2)

steved.
> ---
> Hi,
>
> if you merge, please keep Joey as the author in git :).
>
> Kind regards,
> Petr
>
> utils/mount/fstab.c | 2 +-
> utils/mount/fstab.h | 1 +
> utils/mount/mount.c | 7 +++++++
> 3 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/utils/mount/fstab.c b/utils/mount/fstab.c
> index 8b0aaf1a..146d8f40 100644
> --- a/utils/mount/fstab.c
> +++ b/utils/mount/fstab.c
> @@ -61,7 +61,7 @@ mtab_does_not_exist(void) {
> return var_mtab_does_not_exist;
> }
>
> -static int
> +int
> mtab_is_a_symlink(void) {
> get_mtab_info();
> return var_mtab_is_a_symlink;
> diff --git a/utils/mount/fstab.h b/utils/mount/fstab.h
> index 313bf9b3..8676c8c2 100644
> --- a/utils/mount/fstab.h
> +++ b/utils/mount/fstab.h
> @@ -7,6 +7,7 @@
> #define _PATH_FSTAB "/etc/fstab"
> #endif
>
> +int mtab_is_a_symlink(void);
> int mtab_is_writable(void);
> int mtab_does_not_exist(void);
> void reset_mtab_info(void);
> diff --git a/utils/mount/mount.c b/utils/mount/mount.c
> index 91f10877..92a0dfe4 100644
> --- a/utils/mount/mount.c
> +++ b/utils/mount/mount.c
> @@ -204,6 +204,13 @@ create_mtab (void) {
> int flags;
> mntFILE *mfp;
>
> + /* Avoid writing if the mtab is a symlink to /proc/mounts, since
> + that would create a file /proc/mounts in case the proc filesystem
> + is not mounted, and the fchmod below would also fail. */
> + if (mtab_is_a_symlink()) {
> + return EX_SUCCESS;
> + }
> +
> lock_mtab();
>
> mfp = nfs_setmntent (MOUNTED, "a+");
>

2019-11-22 16:27:51

by Petr Vorel

Subject: Re: [nfs-utils PATCH 1/1] mount: Do not overwrite /etc/mtab if it's symlink

Hi Steve,

> On 11/20/19 1:35 PM, Petr Vorel wrote:
> > From: Joey Hess <[email protected]>

> > Some systems have /etc/mtab symlink to /proc/mounts. In that case
> > mount.nfs complains:
> > Can't set permissions on mtab: Operation not permitted

> > See https://bugs.debian.org/476577

> > This change makes mount.nfs handle symlinked /etc/mtab the way
> > umount.nfs and util- linux handle it.

> > Cc: Chuck Lever <[email protected]>
> > Signed-off-by: Joey Hess <[email protected]>
> > [ pvorel: took patch from Debian, rebased for 2.4.3-rc1 and created commit
> > message. Patch is also used in Gentoo. ]
> > Signed-off-by: Petr Vorel <[email protected]>
> Committed... (tag: nfs-utils-2-4-3-rc2)
I'm sorry for introducing a regression.

Send a patch fixing this.
https://patchwork.kernel.org/patch/11258155/

> steved.

Kind regards,
Petr